1. Field of the Invention
The present invention relates to a power semiconductor module and semiconductor power converter provided with the power semiconductor module.
2. Description of the Related Art
In general, an electric vehicle or hybrid car is provided with an inverter device as a semiconductor power converter configured to convert DC power to AC power and supply the AC power to a motor. For example, a three-phase inverter device includes three power semiconductor modules corresponding to the U-phase, V-phase, and W-phase. In such an onboard semiconductor power converter, downsizing, cost reduction, and improvement in cooling efficiency are indispensable. In order to achieve such an object, downsizing, cost reduction and improvement in cooling efficiency of the power semiconductor module which is a main component of the semiconductor power converter become important.
According to a semiconductor power converter disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication No. 2007-68302, a power semiconductor module is provided with a first conductor, second conductor, and third conductor each of which is formed of a conductive metal, and a radiator including a joint surface joined to these conductors. The positive electrode side of an insulated gate bipolar transistor (IGBT) and diode which are semiconductor elements constituting an upper arm of one phase is joined to the first conductor. The negative electrode side of an IGBT and diode each constituting a lower arm of the one phase is joined to the second conductor. Further, the third conductor is arranged between the first conductor and second conductor, and is joined to the negative electrode side of an IGBT and diode each constituting the upper arm, and the positive electrode side of an IGBT and diode each constituting the lower arm. The first conductor and second conductor function as a positive electrode, and negative electrode, respectively, and third conductor functions as an AC output electrode. Each IGBT is provided with a plurality of input/output terminals such as an emitter sense terminal.
Further, each of the first to third conductors is arranged on a radiator in such a manner that joint surfaces at which the conductors are joined to the semiconductor elements are not parallel with the joint surface between the radiator and the conductors. By virtue of the configuration described above, there is provided a power semiconductor module and semiconductor power converter in each of which cooling efficiency and manufacturability are improved.
The three-phase semiconductor power converter configured in the manner described above includes one power semiconductor module for each phase, i.e., three power semiconductor modules in all. When such a semiconductor power converter is used in a two-motor hybrid system provide with two motors, in total six power semiconductor modules, i.e., three power semiconductor modules used for one motor, and three power semiconductor modules used for the other motor are required. For this reason, the footprint of the power semiconductor modules is large, this being an obstacle in the downsizing of the overall device. Further, the thermal resistance of the semiconductor power converter is large as a whole, and improvement in the cooling ability is desired.
The plurality of IGBTs calorific values of which are each larger than that of the diode are arranged to face each other with the third conductor interposed between the IGBTs. In this case, heat components conducted from both the IGBTs to the third conductor interfere each other, whereby heat is liable to be accumulated in the third conductor. As a result of this, the thermal resistance of the semiconductor element is made high, and the improvement in the cooling efficiency of the power semiconductor module is lowered.
Further, in the power semiconductor module configured as described above, both the electrode surfaces of the switching element such as the IGBT are joined to the conductor, and emitter sense terminals are provided to the switching elements. In this case, the emitter sense position is in the vicinity of the emitter electrode surface of the switching element, and the inductance on the emitter side becomes substantially zero. As a result of this, when the switching element is driven, a phenomenon in which the current and voltage of the switching element vibrate occurs. When such vibration of the current and voltage occurs, it becomes difficult to stably drive a motor and the like by using the power semiconductor module.